Variable data digital pantographs

ABSTRACT

A variable data pantograph is formed by receiving a variable data string and retrieving at least one character representation from a vocabulary of character representations stored in memory. The retrieved at least one character representation corresponds to the variable data string. Each of the character representations in the vocabulary include a foreground region including a character shape and a background region suitably sized and arranged for encompassing the foreground region. The background region incorporates a first pattern of elements and the foreground region incorporates a second pattern of elements. The retrieved at least one character representation is assembled to form a variable data pantograph, whereby when the variable data pantograph is rendered in an original document, the foreground and background regions are similar in tone, the foreground and background regions being substantially less similar in tone in a copy of the original document to render the character visible.

BACKGROUND

The exemplary embodiment relates to the protection of documents. Itfinds particular application in connection with a method forincorporating variable data in documents which become visible when thedocument is copied.

As the quality of color copiers has improved, it has become easier togenerate copies of a document which are indistinguishable from theoriginal document. In many instances, the unauthorized copying ofdocument content can have serious implications. For example, there is aconcern that color copiers could be used to reproduce securitydocuments, such as checks, stock certificates, automobile titleinstruments, and other documents of value, for illegal purposes.

One method which is used to authenticate documents and to reduce theunauthorized copying employs what is commonly called theVOID-pantograph. Common techniques for creating pantographs involveforming printed dots (or other elements) of two different sizes andfrequencies, which are used to create regions of similar tone,corresponding to a textual warning and background, respectively, in anoriginal (authentic) document. Tone refers to the visual appearanceproduced by halftone dots, bars, or marks which cover at least a portionof a printed area and which usually have a frequency that is measured indots, lines, or marks per inch. To provide constant tone, the smallerelements have a higher frequency than the larger elements. Because thetone of the textual warning and the tone of the background pattern areselected to be the substantially the same, these two regions have asimilar visual impact on an observer of the original document, and thetextual warning is not readily perceived.

On copying, however, the situation changes. Since the response of animage sensor employed in the scanner is different from the response ofthe human visual system, changes in the relative tone of the twodifferent areas will appear. These changes are due to the differentfrequency response of the sensor (with respect to the human eye) andalso due to other, normally non-linear, effects, such as a detectionfloor or threshold, where signals below a certain level are simply“lost.” In general, the high frequency components are more stronglyaffected and attenuated. The difference in response of the scannerexpresses itself as a relative change in tone in the copy and thus thehitherto invisible textual warning becomes visible. For example, in theresulting copy, only the larger printed dots are apparent. These largerdots spell out the word “void,” or other pre-determined textual warning.

In current techniques, the pantograph is applied to the substrate tocreate a pre-printed carrier. An image to be protected is then appliedto the pre-printed carrier.

These methods have generally been successful in protecting documents,and are sometimes combined with other techniques, such as the use ofcamouflage patterns, and the like. However, they are static in natureand thus in general are limited to generally valid, partly nondescriptwords like “void” or “copy.”

There remains a need for a system and method for creation of a dynamicpantograph based on variable input data which enables document-specificor owner-specific data to be incorporated into the pantograph.

INCORPORATION BY REFERENCE

The following references, the disclosures of which are incorporatedherein in their entireties by reference, are mentioned:

U.S. Pat. No. 4,168,088 issued Sep. 18, 1979, entitled PROTECTEDDOCUMENT AND METHOD OF MAKING THE SAME, by Somlyody, discloses documentfor preventing unauthorized copying having on a top surface, backgroundprinted matter made up of small areas of substantially the same size andshape. A warning word is printed on the top surface and blended with thebackground printed matter. The warning word is made up of small areas ofsubstantially the same shape as the background but of a different sizesuch that the warning word cannot be detected by a viewer, but will bevisible upon reproduction by a copying machine.

U.S. Pat. No. 4,210,346, issued Jul. 1, 1980, entitled PROTECTEDDOCUMENT BEARING WATERMARK AND METHOD OF MAKING, by Mowry, Jr. et al.,discloses security document adapted for use with a xerographic colorcopier having a lens reproduction system which has a reproductiondensity threshold which at normal operator accessible copier settingsreproduces dots of a tone density which are larger than the reproductiondensity threshold and which does not resolve and consequently does notreproduce dots of a tone density which are smaller than the threshold.The document includes a substrate and a security background printed onthe substrate which includes a warning mark composed of a dot pattern ofa plurality of relatively large dots patterned so as to comprise thewarning mark. The pattern is surrounded by a plurality of spaced smalldots. The dots are registered so as to be in phase with the large dotsbeing spaced a distance which is a multiple of the distance between thesmall dots. The large dots and small dots are aligned as a parallelscreen with the pitch of the smaller dots being twice the pitch of thelarge dots. The large dots and smaller dots are camouflaged by acamouflage overlay pattern printed as a visually confusing and obscuringpattern.

U.S. Pub. No. 20070139681,published Jun. 21, 2007, entitled PRINTEDVISIBLE FONTS WITH ATTENDANT BACKGROUND, and U.S. Pub. No. 20070139680,published Jun. 21, 2007, entitled VARIABLE DIFFERENTIAL GLOSS FONT IMAGEDATA, both by Reiner Eschbach, et al., disclose methods for supplyingdifferential gloss or other correlation mark text into a document imagevia a font definition, particularly as when desired in the employ ofrendering variable data. A font character is selected and sub-sampled.The sub-sampled result is then scaled up into a full size result. Afirst halftone cell having a first anisotropic structure orientation isselected and applied to the full size scaled font result while a secondhalftone cell having a second anisotropic structure orientation isapplied to the surrounding background around the full size scaled fontresult to create a gloss font or other correlation mark character. Thisfull gloss font character or correlation mark character is then storedas a font representation as callable by the digital front end of aprinting apparatus.

BRIEF DESCRIPTION

In accordance with one aspect of the exemplary embodiment, a method offorming a variable data pantograph includes receiving a variable datastring and retrieving at least one character representation from avocabulary of character representations stored in memory. The retrievedat least one character representation corresponds to the variable datastring. Each of the character representations in the vocabulary includesa foreground region including a font body image shape and a backgroundregion suitably sized and arranged for encompassing the foregroundregion. The background region incorporates a first pattern of elementsand the foreground region incorporates a second pattern of elements. Theat least one character representation is assembled to form a variabledata pantograph. When the variable data pantograph is rendered in anoriginal document, the foreground and background regions are similar intone. The foreground and background regions are substantially lesssimilar in tone in a copy of the original document to render the fontbody image shape visible.

In accordance with another aspect, a method of generating a fontrepresentation includes receiving a set of characters to be representedin the font representation and, for each of the characters, rasterizingthe character at a reduced resolution to form a grid in which eachlocation in the grid is designated as ON or OFF. For each ON location, afirst base pattern comprising a first element is assigned and for eachOFF location, a second base pattern comprising a second element isassigned. The character representation is stored in memory, a set of thestored character representations forming the font representation. Thefirst and second base patterns are selected to provide regions ofsimilar tone when rendered in an original document, which regions beingsubstantially less similar in tone in a copy of the original document torender the character visible.

In accordance with another aspect of the exemplary embodiment, a systemfor generating a variable data pantograph includes a reception componentwhich receives a variable data string. A memory stores a vocabulary ofcharacter representations, each of the character representations in thevocabulary including a foreground region including a font body imageshape and a background region suitably sized and arranged forencompassing the foreground region. A generation component retrieves aselected at least one of the character representations from thevocabulary which is/are to form a variable data pantograph correspondingto the received variable data string. Optionally, an applying componentapplies the variable data pantograph to an input image, whereby when thevariable data pantograph is rendered in an original document, theforeground and background regions are similar in tone, the foregroundand background regions being substantially less similar in tone in acopy of the original document to render the character visible.

In accordance with another aspect, an electronically stored vocabularyof character representations resides in memory for use in a printingsystem. Each of the stored character representations includes aforeground region having a character shape and a background regionsuitably sized and arranged for encompassing the character shape. Afirst pattern of elements is incorporated into the characterrepresentation to define the foreground region and a second pattern ofelements is incorporated into the character representation to define thebackground region, whereby when the character representation isincorporated in a variable data pantograph which is rendered in anoriginal document, the foreground and background regions are similar intone, the foreground and background regions being substantially lesssimilar in tone in a copy of the original document to render thecharacter visible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a greatly enlarged view of a stored character representationsuitable for use in creation of a variable data pantograph in accordancewith a first aspect of the exemplary embodiment;

FIG. 2 illustrates a method for the creation of the variable datacharacter representation of FIG. 4;

FIG. 3 graphically illustrates some of the steps in the method of FIG.2;

FIG. 4 illustrates an exemplary variable data pantograph which may begenerated by concatenating a character representations of the type shownin FIG. 1;

FIG. 5 illustrates three different rasterized characters;

FIG. 6 illustrates a portion of an original document incorporating thevariable data pantograph of FIG. 4;

FIG. 7 illustrates a portion of a copy of the original documentincorporating the variable data pantograph of FIG. 4;

FIG. 8 illustrates a system for incorporating a variable data pantographin an original document, in accordance with a second aspect of theexemplary embodiment; and

FIG. 9 illustrates a method for incorporating a variable data pantographin an original document, in accordance with a third aspect of theexemplary embodiment.

DETAILED DESCRIPTION

In the following, a system and method for creation of a pantograph isdescribed which can eliminate the limitations of existing methods bymaking the pantograph a variable data imaging element that can becreated dynamically and that can encapsulate document content in thedocument protection. The exemplary method allows the textual warning tohave a generalized capability, such as “Copied from an Original owned byABC Corp. ” or “If found contact 555-1234” or any other variable datastring. It will be readily appreciated that the deterrent effect of sucha personalized textual warning can be greater than for a static,nondescript warning. Consequently, the likelihood that such a documentmay be negligently or intentionally furnished to an unauthorized partyis considerably diminished.

As will be appreciated, when requesting, say the letter “A”, in any oneof a set of various font representations available in the system, thehuman reader will not perceive anything resembling an alphanumericcharacter. Rather in the printed original document, the user willperceive an area (generally rectangular) of constant tone and color. Itis only after copying or scanning that the area changes to exhibit ahuman readable “A”, in this example. Close examination of the constanttone area, however, e.g., under a microscope, will allow an expert to“trace” the outline of the character by tracing the boundary between twodistinct pattern areas of high and low frequency printed elements.

Aspects of the exemplary embodiment relate to a method and system forgenerating a digital pantograph that permits the incorporation ofvariable data and that can be created in real-time. This can be achievedby creating a pantograph vocabulary of one or more font representations,each font representation comprising a finite set of characterrepresentations. These character representations can be arbitrarilycombined into a meaningful variable data sequence: a variable datapantograph.

Each of the character representations includes two regions: a firstregion, which can be considered as the foreground region having a fontbody image shape, and a second region or background region, whichconstitutes a field area that is suitably sized and arranged forencompassing the font body image shape. The foreground and backgroundregions are abutting and are sparsely populated with elements whichprovide similar tone to the regions in an original document but whichrespond differently to copying such that differences in tone then becomeapparent, making the font character represented by the characterrepresentations visible.

Tone refers to the apparent gray level. In the case of halftoning, tonerefers to the visual effect produced by halftone dots, bars, or markswhich cover a portion of a printed area and which usually have afrequency that is measured in dots, lines, or marks per inch. Theelements are sufficiently tiny that they are blended into a smooth toneby the human eye. Because the tone of the foreground area representing acharacter and the tone of the background pattern are selected to be thesame, these two areas have much the same visual impact on an observer ofthe original document, and the character or phrase is not readilyperceived. The optics of color copiers usually exhibit a differentresponse characteristic to that of the human eye. For example, copiersare typically unable to accurately reproduce relatively small or highfrequency halftone dots, lines, or other elements. As a consequence,reproduced copies of the original document will have a noticeabledifference in tone, rendering the previously essentially unrecognizablecharacter(s) visible. It is well known in the art that the imagereproduction of a copier/scanner is influenced by the optics employed,the sensor elements, the image processing, etc. For simplicity we willnot distinguish the components in the description, since the overallattribute is the resultant difference in tone of the copy/scan.

The variable data to be represented can take the form of charactersselected from a finite set of characters which is referred to hereingenerally as a vocabulary, which may be variably arranged in anyselected order to form words, phrases, number sequences, other charactersets, or any desirable combination thereof.

In various aspects, a set of character representations is electronicallystored in memory for use in a printing system. The set of storedcharacter representations may form a pantograph vocabulary wherebyselected character representations may be retrieved from memory andarranged, e.g., concatenated to form a variable data pantographrepresenting a selected text string, such as a word or phase, orarranged to form other patterns of character representations in arendered document. The character representations in the vocabulary mayrepresent characters in a particular font. As will be appreciated, setsof characters for different fonts may be provided, i.e., a plurality offont representations.

The term “font” is used herein to indicate the Page Description Language(PDL) concept of a font, where the font can contain standard ASCIIcharacters, but also other characters, e.g. Kanji, symbols, small icons,lines, bar codes and other elements that are commonly represented in abinary state modus, as illustrated, for example, in U.S. Pub. No.20070139681, incorporated by reference. The exemplary vocabulary canthus incorporate, for example, the letters of any alphabet (such asLatin, Greek, Cyrillic, a combination thereof or the like) and/ornumbers, e.g., the numbers 0-9. Other characters, such as common icons,arrows, and other symbols may also be included in the vocabulary.

FIG. 1 depicts an exemplary character representation 10 (hereillustrated as a representation of the letter A) which can be producedby the method shown in FIGS. 2 and 3. Such a character representation 10can be stored in memory for subsequent retrieval and assembly with othercharacter representations to form a variable data pantograph 12 of thetype shown in FIG. 4.

The character representation 10 includes a background region 14, whichforms a field area, and a foreground region 16, entirely containedtherein and contiguous therewith. The union of background and foregroundregions 14, 16 may be of any suitable shape, such as rectangular,hexagonal, or the like which permits a sequence of characterrepresentations to be seamlessly arranged in any desired order forrendering as a void pantograph. For convenience, rectangular shapes areemployed for the background 14. The foreground region 16 has a shapewhich corresponds generally to that of a character to be represented bythe character representation 10. As will be appreciated from thefollowing description, the terms “foreground region” and “backgroundregion” are used for convenience to identify two regions of a characterrepresentation which are of similar tone but which respond differentlyto copying and are not intended to imply that the regions aredistinguishable in an original document or that they need to be storedas separate elements in a data structure.

A first pattern 18 of elements 20 is applied in the background region 14to fill the background region and a second pattern 22 of elements 24 isapplied in the foreground region 16. The patterns 18, 22 may be formedfrom dots, lines, or other elements 20, 24. In the illustratedembodiment, the elements 20, 24 are dots of different sizes. The dotsmay be as described in U.S. Pat. No. 4,210,346. The arrangements of dotscan be created by a design process, as described in further detailbelow.

The foreground region 16 has a similar tone to the background region 14.In particular, the background region has elements 20 of a first size(which may be expressed, for example, as an object size or as the numberof pixels in a halftone structure) and a first spacing s₁ (s₁=1/f₁,where f₁ is the frequency, which may be expressed as elements 20 perunit length). The foreground region 16 has elements 24 of a second sizeand second spacing s₂ (s₂=1/f₂, where f₂ is the frequency, which may beexpressed as elements 24 per unit length) the second size beingdifferent from the first size and the second spacing being differentfrom the first spacing. It is to be understood that “unit length” isreplaced by “unit area” for the actual 2-dimensional case. In oneembodiment, the first and second patterns are substantially identicalother than with respect to the size and frequency of the elements. Inother embodiments, the elements may differ in shape, color, or otheraspect while still providing a visibly similar or identical tone in theoriginal document. In some embodiments, any slight variations in toneare masked by introducing a distraction pattern, or camouflage, asdisclosed in above-mentioned U.S. Pat. No. 4,210,346, incorporated byreference.

In the exemplary embodiment, the elements 20, 24 of the two regions 14,16 are simultaneously encapsulated inside each of the characterrepresentations 10. The entire font character representation can thus bestored as a single data set. The rendering system is thus not aware ofthe foreground/background distinction which is described hereinprimarily for purposes of human understanding. To the rendering system,a rectangular area is simply rendered containing two differentlytextured regions.

The elements 20, 24 respond differently to copying, such that in acopied document, the regions 14, 16 are no longer of similar tone butdiffer in tone. As a result, a copy of the original document made on acolor copier displays a cancellation term. In one embodiment, elementsof one of the first size and the second size are sufficiently small suchthat, when in an original document incorporating the characterrepresentation, they are not reproduced by a color copier at aparticular copier setting while elements of the other of the first sizeand the second size are sufficiently large such that they are reproducedby the color copier at the particular copier setting.

The exemplary rectangular background region 14 is of sufficient width wto provide a character-area of toroidal symmetry (left side 30 matchesup to the right side 32, using a sparse repeat pattern of elements 20(with a spacing corresponding to a frequency f₁). The toroidal symmetryallows the seamless stitching of arbitrary tiles. The sparse repeatpattern facilitates the “unobtrusive nature” as well as easier placementof character outlines. The character pattern 22 for foreground region 16is designed using a related sparse repeat pattern of elements 24 (with aspacing corresponding to a frequency f₂) with a clear distinction inexpected copier response. This distinction can be generated by varyingfrequency, shape, orientation or any combination thereof.

In the exemplary embodiment, the character representation 10 is definedby an imaginary n×m grid 34 in which each square 36 of the grid has oneof two (or more) dot patterns assigned to it wherein the dots 20, 24 areentirely contained within the respective grid square. As will beappreciated, in FIG. 1, the grid lines are shown for clarity only andare not a part of the stored character representation 10. In this way,all characters can be created as individual character representations 10and embedded as a pantograph font and can be requested using standardworkflow mechanisms.

FIGS. 2 and 3 illustrate one embodiment of a method for creating acharacter representation 10 of the type shown in FIG. 1. It isunderstood that some of the steps of the method do not need to beperformed in the order illustrated and may be parallelized,interchanged, or new or different steps employed. The method begins atS100.

At S102, font attributes for a character 38 to be represented areselected, such as character set, shape, size, etc. For example, in FIG.2, the font type “Arial” and the font size 24 are selected forgenerating a character representation of the character “A,” in aselected font representation, as shown at (1) in FIG. 3. Here,“character” refers to a logical entity that is represented in one ofmany known forms, such as outlines, splines or any other graphical orimage description.

At S104, a base pair of patterns 18, 22 of similar tone is selected.Each of the base patterns 18, 22 is formed of a respective one of thetwo (or more) types of elements 20, 24, which may be arranged singly orin combination at a selected spacing and orientation. The exemplarypatterns 18, 22 are of the same size and shape so they can be tiledtogether to form the character representation. At this stage, the toneis only defined in terms of size (d₁, d₂) and spacing/frequency of theelements. At a later stage, it may be modified with actual colordescriptors, such as “cyan”, “red”, etc. In general, the two basepatterns 18, 20 selected for the regions 14, 16 differ in at least oneof: size of elements; number of elements per pattern; spacing/frequencyof elements; and shape of elements.

For example, as shown in FIG. 3, a first pattern (a) having a singlecentrally spaced element 20 with a spacing s₁ and size d₁ is selected asthe base pattern 18 for the background 14 of the characterrepresentation 10 (here, the “off” pixels of a character image). Asecond pattern (b) or (c) with elements 24 having a spacing s₂ and sized₂ is selected as the base pattern 22 for the foreground region 16 ofthe character representation 10 (here, the “on” pixels). The second basepattern 22 includes a plurality of the second elements 24, four in theillustrated embodiment, being equivalent to a “doubling” of the linearcomponent as defined above. The second base pattern 22 may have aplurality of optional configurations as shown at (b) and (c).

As will be appreciated, the elements 20, 24 are shown much larger inFIG. 3 than the elements will appear in the printed document. In thisexemplary description, patterns (a) and (c) have been selected for thebase pair 18, 22. While the elements 20, 24 are represented as circles,in other embodiments, they may be selected from a set of rasterized baseelements as illustrated in FIG. 3 at (4). Each of the second basepatterns (b) (c) is configured to have the same visual tone as the firstbase pattern 18 when embodied in a printed document. The base patterns(a), (b), (c) may thus each have the same overall gray level. Forexample, as illustrated at (4), each pattern has the same number(twelve) of on “ON” pixels in the idealized case.

As will be appreciated, the exemplary method is not dependent on themanner in which the regions 14, 16 of the character representation arecreated and that the exemplary patterns 18, 22 are but one way ofgenerating the character representation which facilitates the creationof individual character representations in a standardized way such asthrough Xerox FreeFlow™ VIPP Specialty Imaging.

At S106, for each character 38 to be represented as a characterrepresentation 10, the character is rasterized to form a rasterizedcharacter image 40. The rasterizing is generally performed at a reducedresolution from that normally used for the character 38. For example, asshown at (3) in FIG. 3, the character image “A” is rasterized in a 10×8pixel grid, although larger or smaller grids are also contemplated. Ingeneral, a reduction in resolution by at least a factor of three in eachdimension is convenient, and in one embodiment, a factor of at leastfour, such as about eight may be used. Thus, for example, a character“A” which is generally stored as an 80×64 pixel data structure in agiven font representation may be readily reduced to a 10×8 pixel grid bycombining a block of 64 pixels into one pixel of the grid.

The purpose of the rasterization is to create a grid of pixel locations36 (here rectangles) which are each large enough to receive one of thebase patterns 18, 22, and thus the reduction in resolution may vary,depending, for example, on the pixel size of the original character 38and the rendering capabilities of the printer, and so forth.

With reference now to FIG. 5, which shows by way of example, grids 34for the characters A, §, and j, the pixel height of the grid (13 pixelsin the exemplary embodiment) may be a constant for all characterrepresentations in the selected font representation. This is similar tothe common point definitions used in printing, where the point number(e.g., 12 point) represents the lead height of classical letter setting.To allow small characters to be represented (as well as characters witha defined descender which extends below the line) while retaining thesame pixel height for each grid, the grid for any given character mayinclude one or more blank rows 42, either at the top or bottom of thegrid 34 or both. Additionally, a spacer row or rows may be incorporated,e.g., at the top and at one or both sides, which is always blank, sothat the character representations can be tiled vertically as well ashorizontally without contact between respective foreground regions 16.Thus, while in rasterization, the letter “A” may be reduced inresolution to an 8×10 grid, the letter A is appropriately located in an8×13 grid 34, for example, to ensure that all characters in the set canbe represented at constant grid height of m pixels.

As also illustrated in FIG. 5, the pixel width of the grid may vary,depending on the particular character to be represented. Thus, forexample, the grid for the character “A” is 8 pixels in width, while thecharacter “j” is only 4. As will be appreciated from FIGS. 2 and 5, thegrids at reduced raster automatically enforce the required toroidalsymmetry, thereby ensuring that character representations can beseamlessly tiled in two dimensions.

At this stage, the rasterized character images 40 in the set typicallystill have a human-recognizable form. Each pixel location in the grid 34can assume one of two states, “ON” or “OFF.” For simplicity in FIGS. 3and 5, the character pixels are described by “OFF” (white) for thebackground and “ON” (black) for the foreground (character). As will beappreciated, steps S102-S104 can be performed in advance for allcharacters in the set. The actual character image 40 is then retrievedfrom memory at S106.

Returning once more to FIG. 2, at S108, each character image pixel inthe “OFF” state is replaced with the first base pair pattern (a) andevery pixel in the “ON” state is replaced with the second base pairpattern (c). See, for example at (5) in FIG. 3. Each base pattern (a),(b), (c) is the same size and shape is thus configured for substitutionwith any pixel 36 of the reduced resolution rasterized character 40. AtS110, the character raster image 10 is then stored inside the newpantograph font at the logical location of the input character in theinput font. In this example, a so-called Type 3 Font is used.

The steps are repeated as necessary for every character of the inputfont.

The method ends at S112.

It should be noted that the font character 38 is rasterized to thereduced resolution in a way that the combination of the lower resolutionwith the base pattern size results in the intended size at printresolution. The selection of the font (S102) has an impact on theoverall variable data pantograph usability, since some graphical designsof fonts do not favor rendering at a reduced resolution. Although moreelaborate graphical characters can be used, it is generally moreeffective if a simpler visual representation of the logical character isemployed. For simplicity, the rasterization effect illustrated at (4) isnot shown in (5).

The result has intended print resolution, since the base pattern pairswill be rendered at print resolution, whereas the font image as renderedat the lower resolution defined by the ratio of print resolution andbase pair periodicity. This conversion to higher resolution might beperformed at this step by using the appropriately rastered versions ofthe base pairs, or at a later step by rasterizing the graphicdescription of the base pairs.

As will be appreciated, more than one character representation 10 may bestored for representing the same character 38. Additionally characterrepresentations may be stored for different character sizes or fontstyles. For example, character representations may be separately storedfor font size 36 point and font size 96 point and characterrepresentations may be separately stored for generating variable datapantographs with character representations similar to Times New Romanand Arial characters. Each of the plural character representations maybe individually tailored to maximize the blending of foreground andbackground regions so that they appear similar in tone.

The character representation 10 may be stored in any convenient format.A suitable character representation format is one that that isefficiently handled by a DFE (Digital Front End) such as DocuSP® thatuses the font in a variable data application such as VIPP® (VariableData Intelligence Postscript Printware) and other various documentmanagement software, such as FreeFlow™.

In one embodiment, the elements 20, 24, when rendered on print media,may be less than 1 mm in size, e.g., average diameter, such as about 0.3mm or less. The elements 20 may have a size (e.g., number of pixels)which is at least twice that of elements 24, or vice versa.

While in the exemplary method, the background and foreground regions 14,16 of the stored character representation are created by tiling repeatpatterns 18, 22, in other embodiments, the dots 20, 24 may be applied tothe foreground or background region as a whole, such that some of thedots may be cut at the edges of regions 14, 16. In such an embodiment,the design of the individual foreground characters is such that itavoids cutting through the repeat pattern of the regions 14, 16 as muchas possible and/or allows “matched” cutting so that the cut smallerelements 24 of the foreground 16 contact the cut larger elements 20 ofthe background region 14, where possible. The size and position of theforeground character 16 may be selected to provide similar phasing ofthe two patterns of dots 20, 24, along with a clear outline of theletter. Otherwise, non-linear effects of the human visual system may notallow the ‘letter’ to blend sufficiently into the ‘background’ to avoiddetection in the original document.

In yet other embodiments, the character representations 10 are stored asbitmaps similar to grid 40 and the different patterns formed bysubstitution of patterns 18, 22 at the time of printing or by halftoningthe regions 14, 16 with two different halftone screens, as described,for example, in U.S. Pub. No. 20070139681,incorporated by reference.

As shown in FIG. 4, a variable data pantograph 12 may be generated bycombining two or more of the stored character representations 10. InFIG. 4, four character representations 10A, 10B, 10C, and 10D arearranged in sequence to represent the word TEST, by way of example,although the possibilities are virtually limitless. The backgroundregion 14 for each of the character representations 10A, 10B, 10C, and10D may be of the same height h as that of the other characterrepresentations in the same font representation in the stored finitevocabulary. Different font representations may have a different heighth. The height h may be an integer multiple of the pattern spacing forperiodicity reasons. For example, if the background pattern 18 is thecoarser of the two patterns, the height h may be an integer multiple ofthat periodicity. This requirement guarantees that two lines of textvertically abutting will do so without a visual artifact at the boundarylocation. The background region may similarly have a width w that is afunction of the size of the grid elements 36 (which in the equalsfrequency of elements 20. For different characters, different characterwidths w may be appropriate, as shown in FIG. 5. This may be describedas a toroidal symmetry requirement for each character representation inthe font representation.

In the illustrated embodiment, each character representation 10A, 10B,10C, and 10D corresponds to a single character 38, such as a letter, butit can readily be envisaged that a character representation may bestored which includes several foreground regions 16, each representing adifferent letter. For example, one character representation could bestored in memory corresponding to the entire word VOID. Additionally, toprovide spaces between words one or more “blank”representations may bestored which each includes the background (or foreground) region only.

As with conventional void pantographs, the variable data pantograph 12illustrated in FIG. 4 may be utilized, for example, to provide securityinformation for a ticket, coupon, or the like, to provide an indicia asto the source of the image, to provide personalized information in massmailings, or to provide time varying information, such as a date onwhich the image is printed, and may include job processing/integritynumbers, bar-codes, company trademarks or logos, or the like. Variabledata pantographs applied to such uses discourages falsification or fraudwhile serial numbers or other changing characters allows for tracking.In one embodiment, a variable data string is generated as a function ofthe IP address or other information identifying the workstation/usersending the original document to a printer such that an unauthorizedcopy of the document can be traced back to the person who printed theoriginal document. For example, the simple “VOID” message can beimplemented with character representations which provide trackinginformation, such as “This document leaked by J. Doe”.

The character representation 10 has an associated font color, upon whichthe standard color operations can be performed. In general, foregroundand background regions 14, 16 have the same color. This means that inmost cases the character representation 10 will have but a single color.For example, in the rendered document, both the foreground andbackground regions may be formed with the same color separation, such ascyan, magenta, cyan, or yellow. By selection of patterns of elements 20,24 which yield similar tone in an original document, as viewed by theunaided eye of a casual observer, variable data can be easilyincorporated by retrieving the stored character representations andassembling them in a selected arrangement.

In the exemplary embodiment, the selected character representations 10are rendered on a substrate, such as paper or plastic, by printing.Therefore, the foreground and background regions 14, 16 appear to havesubstantially the same tone to the unaided eye of an observer. FIG. 6illustrates an exemplary variable data pantograph 12 as it may appear inan original document 50 when rendered on a substrate 52, under highmagnification. The rendered variable data pantograph 12 is formed from asequence of different character representations 10A, 10B, 10C, and 10Dfrom a selected font representation, which have been concatentated tocreate the word TEST, as illustrated in FIG. 4. It will be understoodthat the string “TEST” shown in FIG. 6 is not visible as a difference intone, but as a change in texture under this high magnification. Atstandard size, as it would be used in the present application, thistexture difference is invisible to the human eye and the word would thusnot be readable.

In FIG. 6, by way of example, the same variable data pantograph 12 hasbeen tiled across the substrate surface to form a pattern. Blankrepresentations 54 are used to complete the pattern. The document 50also includes rendered image data 56. In one embodiment, the renderedimage data 56 is rendered with at least one color separation whichdiffers from that used in rendering the variable data pantograph 12. Forexample, the variable data pantograph may be rendered in yellow ink ortoner and the image data in one or more of cyan, magenta, and black inksor toners.

FIG. 7 illustrates a copy 60 of the original document 50 shown in FIG.6. Here, the smaller dots used in generating the foreground region 16were too small to copy effectively and the foreground region 16 appearsblank (or at least much lighter in tone than the background region 14).The exposed variable data string 62 (e.g., TEST), sometimes referred toas a cancellation term, is clearly apparent to the unaided eye.

As illustrated in FIG. 8, a printing apparatus 70 may be provided havingelectronically stored, e.g., in memory 72 accessible to the printingapparatus, a vocabulary 74 of the electronic data characterrepresentations 10 (here illustrated as character representations 1 and2) which can be retrieved and assembled in any desired arrangement, toform a variable data pantograph 12 which is rendered along with an image76, onto a substrate 52 to form an original document 50. The printingapparatus may include a reception component 78 which receivesinformation 80 concerning a variable data string to be represented ascharacter representations, and a generation component 82 for retrievingthe selected data character representations 10 from memory 72, based onthe received information 80, and assembling them in an arrangement inaccordance with the received information. The information 80 received byreception component 78 may include the variable data string to berepresented (such as the sequence of characters of the word VOID) or thereception component 78 may receive the variable data string from anothersource, based on the information 80. The generation component 82 maytile the generated pantograph 12 of character representations in orderto form a pattern of such pantographs over at least a portion of theoriginal document 50 or over the entire document 50. In otherembodiments, only a small area of the image 76 is targeted forincorporation of the variable data pantograph 12. An applicationcomponent 84 incorporates the variable data pantograph 12 into the imagedata 76 to form binary image data for rendering on a marking device or“printer” 86.

Reception component 78, generation component 82, and applicationcomponent 84 may be embodied in software, hardware, or both. In theexemplary embodiment, these are software components comprisingprocessing instructions stored in memory, such as memory 72 or aseparate memory, and which are executed by an associated processor 88.Components 78, 82, and 84, as well as memory 72 and processor 88, eachmay be local to the printing apparatus, as shown, or remote therefrom.

In the illustrated embodiment, the processor 88 is resident in theprinter's digital front end, or DFE. A primary image 76 may be receivedas input data to the processor 88 as is normal. For example, the image76 may be transferred from a remote workstation 90 or input from animage data storage medium, such as a floppy disk, flexible disk, harddisk, magnetic tape, or any other magnetic storage medium, CD-ROM, DVD,or any other optical medium, a RAM, a PROM, an EPROM, a FLASH-EPROM, orother memory chip or cartridge. The primary image data 76 may includeimage data for one or more color channels, e.g., in a portable documentformat. During processing, the primary image data 76 may be stored inmemory 72, which is accessible to the processor 88.

A printing apparatus, as used herein can include any device forrendering a dynamically variable image on print media, such as a laserprinter or a multifunction machine having copying and/or faxing as wellas printing capability. “Print media” can be a physical sheet of paper,plastic, or other suitable physical print media substrate for images.The original document 50 can be a single sheet or set of related sheetsgenerated from electronic document page images, from a particular user,or otherwise related, and the exemplary digital pantograph. An imagegenerally may include information in electronic form which is to berendered on the print media by the printer and may include text,graphics, pictures, and the like. The operation of applying images toprint media, for example, graphics, text, photographs, etc., isgenerally referred to herein as printing or marking. While in theexemplary embodiment, the printing apparatus 70 is described in terms ofa xerographic printer, it is also contemplated that the printer mayincorporate inkjet or other marking technology.

Information 80 may accompany the image 76 in the form of a job ticket,which provides the instructions for generating the variable datapantograph 12. Alternatively, at least some of the instructions 80 maybe embedded in the image 76, for example, using HTML or XML tags. Theinstructions 80 may include parameters of a variable data string to beincorporated, such as one or more of the letters or other characterswhich are to make up the variable data pantograph, the order in whichthey are to appear in the string, the location(s) of the variable datapantograph 12 with respect to the primary image 76, or repetitionpattern or other arrangement of the variable data string on the page, aswell as the color(s) to be used in rendering the variable data string.Alternatively, one or more of the parameters of the variable datapantograph 12 may be selected at the printing apparatus 70 or be storedin memory 72 at the printing apparatus or be received in a file alongwith the incoming primary image data.

In one embodiment, the generation component 82 generates the variabledata pantograph based on the source 90 of the information, such as thename of the workstation user. For example, the generation component 82may configure the variable data string in the general form “printed byX” where X is the name of the workstation user, which is provided byinformation 80.

In another embodiment, a user selection device 92, in communication withthe processor 88 allows a user to provide information 80. The exemplaryuser selection device 92 includes a screen 94, which displays agraphical user interface, and an associated input device 96, such as akeyboard, keypad, touch screen, and/or cursor control device, whichallows a user to select characters to form variable data strings, forexample, by typing a text string on the keyboard 96. For example, theuser may type the variable data string “No copying without authorizationof Jane Doe,” which is to be used to form the variable data pantograph12. In one embodiment, the user can view a representation of thevariable data pantograph 12, superimposed on the image 76, on the screen94. The representation of the pantograph may illustrate the cancelledterm which will appear when the document is copied, rather thanreplicating the variable data pantograph exactly. The user can thendetermine whether the variable data pantograph is properly located, withrespect to the image 76. In one embodiment, the user can changeparameters, such as the pantograph's location, size, repetitionfrequency, color, or the like via the input device 96. As will beappreciated, each of these operations may alternatively take place at alocation remote from the printer, such as at the workstation 90. In oneembodiment, a user interface similar to that disclosed in U.S. Pub. No.20060127117, published Jun. 15, 2006,entitled USER INTERFACE FORDIFFERENTIAL GLOSS IMAGES, by Reiner Eschbach, et al., may be employedas the user selection device 92. The user is instructed to indicate thebase primary image data, and the characters forming the desired variabledata pantograph 12. This data may be displayed for verification andposition adjustment by superimposition of the representation of thevariable data pantograph upon the base image data.

In combining the variable data 12 with the image data 76, a single colormay be selected for the variable data, which is different from the restof the image. Or, where a particular color separation is used for boththe image data 76 and the pantograph 12, the image data may takeprecedence over the pantograph 12, or vice versa.

In one embodiment, the image data 98 thus formed which includes thevariable data pantograph 12 and optionally image 76, such as text,graphics, or the like, may be stored as a digital image data file to berendered by the same or a different printer or marking device from theprinting apparatus creating the digital image file. For example, theimage data file may be stored for later rendering on a printer whichdoes not have software and/or hardware for embedding variable datapantographs in images.

The exemplary processor 88 executes instructions 78, 82, 84, stored inmemory for performing the method outlined in FIG. 9. The processor 88may be embodied as hardware, software or both and may be hosted by anysuitable computing device, such as a PC, such as a desktop, a laptop,palmtop computer, portable digital assistant (PDA), cellular telephone,pager, a programmed microprocessor or microcontroller and peripheralintegrated circuit elements, an ASIC or other integrated circuit, adigital signal processor, a hardwired electronic or logic circuit suchas a discrete element circuit, a programmable logic device such as aPLD, PLA, FPGA, or PAL, or the like. Components of the apparatus maycommunicate via a data control bus 100.

The memory 72 may represent any type of computer readable medium such asrandom access memory (RAM), read only memory (ROM), magnetic disk ortape, optical disk, flash memory, or holographic memory. In oneembodiment, the memory 72 comprises a combination of random accessmemory and read only memory. In some embodiments, the processor 88 andmemory 72 may be combined in a single chip. In one embodiment, memory 72stores instructions executed by the processor 88 for performing theexemplary method as well as the vocabulary 74 and processed image data98.

While particular reference is made to electrophotographic (e.g.,xerographic) printers, suitable printers 86 may also include ink-jetprinters, including solid ink printers, thermal head printers that areused in conjunction with heat sensitive paper, and other devices capableof marking an image on a substrate. In some embodiments, printer 86includes a plurality of marking devices, such that a first markingdevice may apply a first color separation (such as for applying thevariable data pantograph 12) and a second marking device may apply acolor separation (e.g., for applying the image 76).

FIG. 9 illustrates an exemplary method for creating an original document50 incorporating a variable data pantograph 12 in accordance with theexemplary embodiment. It should be appreciated that the method mayinclude fewer, more or different steps and that the steps of theexemplary method need not be performed in the order shown. The methodassumes that a set of character representations 10A, 10B, etc. have beengenerated for the entire vocabulary 74, e.g., by the method of FIG. 3,and stored in memory 72. In general, these preliminary steps areperformed prior to receiving a request to generate an original document50 and thus once performed do not need to be repeated for each originaldocument 50 to be created. In other embodiments, however, they may beperformed later.

The method begins at S200. At S202, an input image to be rendered isinput to the processor 88. For example, a digital image file whichincludes one or more digital images, such as image 76, is received bythe printing apparatus 70, e.g., in the form of a print job. The filemay be received via a network, e.g., from the networked computer 90 orinput from an image data storage medium, such as a floppy disk, flexibledisk, hard disk, magnetic tape, or any other magnetic storage medium,CD-ROM, DVD, or any other optical medium, a RAM, a PROM, an EPROM, aFLASH-EPROM, or other memory chip or cartridge. Alternatively, the filemay be input to a computing device separate from the printer, on whichthe processor 88 is located, or retrieved from an image data storagedevice by that computing device.

At S204, information 80 for generating a variable data pantograph 12 isinput. For example, instructions 80 are received by reception component78. The instructions may include a data string, such as a group ofcharacters, which is to be incorporated into the image as a variabledata pantograph, together with a selected font representation, wheremore than one font representation is available or provide otherinformation from which a variable data string is identified.

At S206, character representations 10 are retrieved from memory 72 inaccordance with the information 80 and assembled to form a variable datapantograph 12.

At S208, a binary image is generated for the color separation to be usedfor the variable data pantograph, together with any image data selectedfor that color separation.

At S210, color binary image(s) for other color separation(s) to be usedfor the image data are generated. At the end of step S210, the entireimage 98 (image data 76 and pantograph 12) has been processed in asuitable format for rendering, e.g., as halftone dots.

At step S212, the halftoned or otherwise processed image 98incorporating the embedded variable data pantograph 12 and primary imagedata 76 is submitted to the output device 86, where it is printed (e.g.,with inks, toners or other marking material) on a blank print mediasubstrate 52 to form an original image document 50. The method ends atS214.

As will be appreciated, the above method is appropriate for characterrepresentations 10 in which the sizes and periodicities of the elements20, 24 are already incorporated into the character representations.Where the character representations are stored in other formats in whichthe regions are simply designated a type of element whose exactcharacteristics (e.g., size, periodicity, and/or locations), aredetermined later, the method may include additional steps, to populatethese regions with elements. For example, first and second halftonescreens may be provided, a respective screen being used for each of theregions 14, 16. The first and second screens may have different screenfrequencies, but may otherwise be identical. A binary image may thus begenerated for the color separation to be used for the variable datapantograph by toggling between first and second screens in accordancewith the foreground and background regions.

The computer implemented steps of the method illustrated in FIGS. 2and/or 9 may be implemented in a computer program product that may beexecuted on a computer. The computer program product may be a tangiblecomputer-readable recording medium on which a control program isrecorded, such as a disk, hard drive, or may be a transmittable carrierwave in which the control program is embodied as a data signal. Commonforms of computer-readable media include, for example, floppy disks,flexible disks, hard disks, magnetic tape, or any other magnetic storagemedium, CD-ROM, DVD, or any other optical medium, a RAM, a PROM, anEPROM, a FLASH-EPROM, or other memory chip or cartridge, transmissionmedia, such as acoustic or light waves, such as those generated duringradio wave and infrared data communications, and the like, or any othermedium from which a computer can read and use.

The exemplary methods disclosed herein may be implemented on one or moregeneral purpose computers, special purpose computer(s), a programmedmicroprocessor or microcontroller and peripheral integrated circuitelements, an ASIC or other integrated circuit, a digital signalprocessor, a hardwired electronic or logic circuit such as a discreteelement circuit, a programmable logic device such as a PLD, PLA, FPGA,or PAL, or the like. In general, any device, capable of implementing afinite state machine that is in turn capable of implementing theflowchart shown in FIG. 2 and/or 9, can be used to implement the methodsfor creation of character representations 10 and for embedding variabledata pantographs 12 in an original document.

In experiments comparing the digitally generated variable pantographswith those formed by preprinting paper with a predetermined analogpantograph which is used for applying an image thereto, the digitallycreated variable pantograph performed well.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A method of forming a variable data pantograph comprising: receivinga variable data string; retrieving at least one character representationfrom a vocabulary of character representations stored in memory, theretrieved at least one character representation corresponding to thevariable data string, each of the character representations in thevocabulary including a foreground region including a character shape anda background region suitably sized and arranged for encompassing theforeground region, the background region incorporating a first patternof elements and the foreground region incorporating a second pattern ofelements; assembling the retrieved at least one character representationto form a variable data pantograph, whereby when the variable datapantograph is rendered in an original document, the foreground andbackground regions are similar in tone, the foreground and backgroundregions being substantially less similar in tone in a copy of theoriginal document to render the character visible.
 2. The method ofclaim 1, wherein the first pattern of elements includes elements of afirst size and a first frequency and the second pattern of elementsincludes elements of a second size and a second frequency.
 3. The methodof claim 2, wherein elements of one of the first size and the secondsize are sufficiently small such that, when in an original documentincorporating the character representation, they are not reproduced by acolor copier at a particular copier setting while elements of the otherof the first size and the second size are sufficiently large such thatthey are reproduced by the color copier at the particular copiersetting.
 4. The method of claim 1, further comprising generating a setof character representations to comprise the vocabulary and storing thecharacter representations in memory.
 5. The method of claim 4, whereinthe generating comprises, for each character representation: rasterizinga font character to define a pixel grid of on and off pixels; applying afirst base pattern to on pixels in the grid; and applying a second basepattern to off pixels in the grid, one of the first and second basepatterns comprising a first element of a first size and the other of thefirst and second base patterns comprising a plurality of second elementssmaller in size than the first element.
 6. The method of claim 5,further comprising reducing a resolution of the font character prior torasterizing the font character.
 7. The method of claim 1, furthercomprising, receiving image data, and incorporating the variable datapantograph into an image to be rendered based on the image data.
 8. Themethod of claim 7, further comprising tiling the variable datapantograph across the image to be rendered.
 9. The method of claim 7,further comprising assigning a first color separation to the variabledata pantograph and assigning a second color separation to the imagedata different from the first color separation.
 10. The method of claim1, wherein the variable data string comprises characters selected from aset of characters and wherein the vocabulary comprises characterrepresentations of each of the set of characters.
 11. The method ofclaim 1, wherein the variable data string comprises at least one ASCIIcharacter and wherein the vocabulary includes character representationsof a set of ASCII characters.
 12. The method of claim 1, wherein theretrieving comprises retrieving a plurality of characterrepresentations, each of the character representations having a widthproportional to a frequency of the elements whereby when the variabledata pantograph is rendered in the original document, the first patternof elements extends seamlessly from the background region of one of thecharacter representations to the background region of an adjacent one ofthe character representations.
 13. A method of generating a fontrepresentation comprising: receiving a set of characters to berepresented in the font representation; for each of the characters:rasterizing the character at a reduced resolution to form a grid inwhich each location in the grid is designated as ON or OFF; for each ONlocation, assigning a first base pattern comprising a first element; foreach OFF location, assigning a second base pattern comprising a secondelement; and storing the character representation in memory, a set ofthe stored character representations forming the font representation;the first and second base patterns being selected to provide regions ofsimilar tone when rendered in an original document, which regions beingsubstantially less similar in tone in a copy of the original document torender the character visible.
 14. The method of claim 13, furthercomprising reducing a resolution of the font character prior torasterizing the font character.
 15. The method of claim 13, wherein thefirst base pattern and the second base pattern each comprise elementsand wherein the first base pattern and the second base pattern differ inat least one of: size of elements; number of elements per pattern;spacing of elements; and shape of elements.
 16. The method of claim 13,wherein the first base pattern and the second base pattern are of thesame size and shape.
 17. A printing apparatus for generating a variabledata pantograph comprising a processor which executes instructions,stored in memory, for performing the method of claim 1 and an outputdevice, which renders the original document, in communication with theprocessor.
 18. An apparatus for generating a variable data pantographcomprising: a reception component which receives a variable data string;memory which stores a vocabulary of character representations, each ofthe character representations in the vocabulary including a foregroundregion including a font body image shape and a background regionsuitably sized and arranged for encompassing the foreground region; ageneration component which retrieves a selected at least one of thecharacter representations from the vocabulary which are to form avariable data pantograph corresponding to the received variable datastring; and optionally, an applying component which applies the variabledata pantograph to an input image, whereby when the variable datapantograph is rendered in an original document, the foreground andbackground regions are similar in tone, the foreground and backgroundregions being substantially less similar in tone in a copy of theoriginal document to render the character visible.
 19. The apparatus ofclaim 18, further comprising an output device which renders the variabledata pantograph on print media to form the original document.
 20. Theapparatus of claim 18, wherein the application component positions thevariable data pantograph relative to received image data of the inputimage.
 21. An electronically stored vocabulary of characterrepresentations residing in memory for use in a printing system, each ofthe stored character representations comprising: a foreground regionhaving a character shape; and a background region suitably sized andarranged for encompassing the character shape, a first pattern ofelements being incorporated into the character representation to definethe foreground region and a second pattern of elements beingincorporated into the character representation to define the background,whereby when the character representation is incorporated in a variabledata pantograph which is rendered in an original document, theforeground and background regions are similar in tone, the foregroundand background regions being substantially less similar in tone in acopy of the original document to render the character visible.
 22. Theelectronically stored vocabulary of claim 21, wherein the first patternand the second pattern have at least one of the same grayscale value andthe same color.
 23. The electronically stored vocabulary of claim 21,wherein the elements of the first pattern and the second pattern differin both size and frequency.
 24. A printing system apparatus havingelectronically stored in memory thereupon the vocabulary of claim 21,whereby selected ones of the character representations are retrievableand arrangeable in a selected order to form a variable data pantographto be incorporated into an image.